1) Field of the Invention
This invention is a method for inhibiting the neuropeptide Y ("NPY") Y5 receptor using a class of substituted .alpha.-alkoxy and .alpha.-thioalkoxyamide compositions. As antagonists of the Y5 receptor, the compositions are useful in treating obese mammals, mammals with bulimia, for treating mammals with obesity related disorders including, but not limited to type II diabetes, insulin resistance, hyperlipidemia, hypertension, polycystic ovarian disease, pulmonary disease, sleep apnea, and for treating mammals suffering from NPY Y5 receptor inhibition related disorders such as memory disorders, epilepsy, dyslipidemia, and depression.
(2) Description of the Art
NPY is a 36 amino acid peptide that is a member of a larger peptide family which includes peptide YY (PYY), and pancreatic peptide (PP). NPY is highly conserved in a variety of animal, reptile and fish species and is found mainly in the central and peripheral sympathetic neurons. Furthermore, NPY is the most prevalent peptide in the mammalian brain where it is found primarily in the limbic regions. NPY has been found to elicit a number of physiological responses including appetite stimulation, anxiolysis, hypertension, and regulation of coronary tone.
NPY is believed to stimulate food intake by activating a hypothalamic eating receptor. Hu et al., J. Bio. Chem., Vol. 271, No. 42 pp.26315-319 (1996) discloses the isolation and identification and the expression cloning of a novel Y-type receptor from rat hypothalamus which the authors designated Y5. According to Hu et al., the localization of Y5 mRNA in critical areas of the brain hypothalamus and other brain regions known to regulate food intake together with an in vitro pharmacological profile consistent with the in vivo feeding data leads those skilled in the art to believe that the Y5 receptor is a primary mediator of NPY-induced feeding. A human homologue of the Y5 receptor has also been identified by Gerald et al., Nature, 382:168-171 (1996) which discloses the isolation, expression and analysis of an NPY Y5 receptor from the rat hypothalamus.
Antagonists of NPY receptors other than the Y5 receptors have been identified. For example, U.S. Pat. No. 5,554,621 discloses NPY antagonists that act on the Y1, Y2, Y3 and other Y1-like or Y4-type receptors. The reported antagonists are dihydropyridine based substituents.
U.S. Pat. No. 5,506,248 also discloses NPY receptor antagonists. The compositions disclosed each include sulphamadyl and arnidino radicals. The disclosed compositions do not include sulfur or oxygen in the backbone structure.
WO 96/16542 discloses genetically modified NPY receptors.
There is evidence that the Y5 receptor of NPY has a pharmacological feeding profile that is unique in comparison to other NPY receptors, namely, Y1, Y2, Y3 and Y4/PP1 because the Y5 receptor response correlates well with in vivo potencies of the standard peptides in the stimulation of feeding. Furthermore, antagonists of other NPY receptors such as Y1 do not necessarily exhibit an inhibitory response when assayed against Y5. In view of the knowledge that NPY plays an important role in eating and other disorders and in view of the knowledge that the Y5 receptor plays an important and unique role in the mechanism of such disorders, there is, therefore, a great need for antagonists of the NPY Y5 receptor. Furthermore, there is a need for antagonists of NPY that specifically target the Y5 receptor.